1. Field of the Invention
The present invention generally relates to a method for enhancing the bond of a bonding wire, and more particularly to a wire bonding structure of a semiconductor package including a non-conductive adhesive material which covers an aluminum pad and seals the whole block portion of a copper bonding wire.
2. Description of the Related Art
Referring to FIG. 1, according to a process for manufacturing a semiconductor package, the technology of wire bonding process widely applied to the electrical connection between a pad 11 of a chip 10 and a pad 13 of a substrate 12 by using a bonding wire 14. Wire bonding process is mainly based on gold (Au) wires, but copper (Cu) wire has an advantage of low cost. Compared with the gold, the copper has better electric conductivity and thermal conductivity, whereby the copper bonding wire has thinner diameter of wire and better dissipation of heat. However, the copper has disadvantage of insufficient ductility and easy oxidation such that the utilization of the copper bonding wire is restricted.
Recently, the copper bonding wire is only applied to a chip pad with a big size or low dielectric material (low-k) of wafer, because the success of the wire bonding process of the copper bonding wire depends on the structural strength of the chip pad. In order to avoid the failure of the wire bonding process of the copper bonding wire, the small size of the chip pad will be limited.
Referring to FIGS. 2 to 4, they depict a conventional method for bonding a copper bonding wire. Referring to FIG. 2, a copper bonding wire 20 is provided by a wire bonding machine, wherein the copper bonding wire 20 has a copper line 22 and a copper ball 24. The copper ball 24 is physically connected to an end of the copper line 22 by a discharging electricity manner or a burning hydrogen manner. Referring to FIG. 3, the copper ball 24 is pressed and then deformed. Referring to FIG. 4, the deformed copper ball 24 is bonded to an aluminum (Al) pad 32 by a vibration process. However, the prior art fails to disclose an additional adhesive force for enhancing the bond between a copper bonding wire and an aluminum pad.
U.S. Pat. No. 7,115,446 B2, entitled “Flip Chip Bonding Method For Enhancing Adhesion Force In Flip Chip Packaging Process And Metal Layer-built Structure Of Substrate For The Same”, discloses that a method for packaging flip chip and a substrate structure can enhance the bond between a chip 50 and substrate 52 by forming bumps 54 on pads 51 of the chip 50 or pads 53 of the substrate 52.
Referring to FIG. 5, although an adhesive layer 56 disclosed in the U.S. Pat. No. 7,115,446 B2 can enhance the adhesive force during the bonding processes of flip chip, the adhesive layer 56 is not applied to the bonding process of the bonding wire. Furthermore, the adhesive layer 56 does not seal the whole bump 54, and thus the adhesive layer 56 cannot generate the effect upon mold lock.
Accordingly, there exists a need for a method for enhancing the bond of a bonding wire capable of solving the above-mentioned problems.